To provide a suitable diagnostic image, it is often necessary to enhance images acquired from the imaging apparatus in order to improve image quality. Fundamental attributes that govern the image quality of a grayscale image include brightness, dynamic range, contrast of detail (or detail contrast), sharpness of edges, and the appearance of noise in the image. It is beneficial to provide a system that enables direct and independent control of these attributes of image quality. Further, a system that enables the control of the detail contrast, sharpness, and noise appearance in a density-dependent fashion is also beneficial.
There have been a number of proposed solutions that address the problem of diagnostic image enhancement. For example, U.S. Pat. No. 5,805,721, entitled “Method and Apparatus for Contrast Enhancement”, inventors P. Vuylsteke and E. Schoeters, issued Sep. 8, 1998 describes a multi-resolution method for enhancing contrast with increased sharpness that includes dynamic range compression and enhancing contrast without noticeably boosting the noise component. The described process enhances detail contrast and sharpness via a multi-resolution method and controls dynamic range compression with a gradation curve to map the processed image into the appropriate dynamic range for the display. Application of the gradation curve will impact both the apparent detail contrast and dynamic range of the displayed image. Hence, both the modifying functions of the multi-resolution processing and the shape of the gradation curve affect the detail contrast in the image. This complex relationship requires that both be adjusted when setting the detail contrast in the image.
U.S. Pat. No. 5,978,518, entitled “Image Enhancement in Digital Image Processing”, inventors Oliyide et al., issued Nov. 2, 1999 and U.S. Pat. No. 6,069,979 (continuation-in-part of U.S. Pat. No. 5,978,518), entitled “Method for Compressing the Dynamic Range of Digital Projection Radiographic Images”, inventor VanMetter, issued May 30, 2000, describe a multi-resolution method for performing dynamic range modification and high-frequency enhancement (including detail contrast). The methods include a tone scale look-up-table that is used to map the image for display rendering. A tone scale look-up-table impacts the dynamic range and contrast of detail in an image. Hence, in this method, the dynamic range and detail contrast of the image depends on both the settings of the frequency modification and the parameters of the tone scale look-up table. It is desirable, instead, to have a less complex arrangement in which a single set of parameters control these attributes independently of each other.
U.S. Pat. No. 6,072,913, entitled “Image Processing Method and Apparatus”, inventor M. Yamada, issued Jun. 6, 2000, describes a multi-resolution method for enhancing frequencies with dynamic range compression. The described invention requires the definition of many functions to control the performance of the algorithm. It does not disclose a set of parameters that directly and independently control all of the fundamental attributes of image quality.
Addressing difficulties not successfully handled by previous image enhancement solutions, commonly assigned U.S. Patent Application Publication No. 2005/0018894 entitled “Method For Rendering Digital Radiographic Images For Display Based On Independent Control Of Fundamental Image Quality Parameters” to Couwenhoven et al. discloses a method for digital image enhancement that enables image characteristics to be adjusted in a substantially orthogonal manner. The Couwenhoven et al. '8894 disclosure teaches modification of image characteristics by decomposing the image according to a number of frequency bands, then independently adjusting gain and related characteristics for each band.
The method described in the Couwenhoven et al. '8894 disclosure allows a degree of independence for manipulation of particular image characteristics without severe impact on other attributes. Thus, for example, the dynamic range can be adjusted with minimal effect on image contrast. It can be appreciated that it would be useful to have capable user interface tools and techniques that work with the frequency bands provided when using the Couwenhoven et al. '8894 technique and related methods that decompose image content according to frequency range.